A woman who falsified drug test results that allowed unscreened truck drivers to travel on the road was sentenced to a year in prison Friday.

Demetri Dearth, 61, of Cottonwood also was fined $2,500 in U.S. District Court in Sacramento for forging drug-testing documents when she was the owner of Advanced Substance Abuse Programs on Hilltop Drive in Redding.

At least 46 times, from March 2009 until February 2010, Dearth accepted urine samples from truck drivers who wanted to get hired as part of the pre-employment process or for random tests and didn't forward them to laboratories, according to U.S. Attorney McGregor Scott.

Instead, Dearth forged test forms that said the results came back negative. She billed her clients for tests that never took place, according to prosecutors.

"It definitely caused us some trouble," said Jason Lindell, the office manager for Boyd Transportation in Cottonwood.

Boyd Transportation and Foothill Ready-Mix of Red Bluff were two of Dearth's more than 80 clients that included aviation, construction, logging and education businesses.

A Foothill Ready-Mix spokesman declined to give details, but Lindell said his business was the one that tipped authorities to Dearth's wrong-doing.

This image shows a page from the 17-page indictment against Demetri Dearth in 2013.(Photo: Image from court documents)

Office workers noticed a discrepancy in testing forms — some of them looked different.

"The results were made to look like a form from an official lab," Lindell said.

When the front office checked with the laboratory, they discovered the lab had never done the tests. Dearth also forged the signature of a doctor trained in substance abuse who is supposed to give explanations for positive drug results, prosecutors said.

By the time the fraud was discovered, which involved up to 20 employees at Boyd Transportation, the truck drivers had been on the road for several months.

Boyd's commercial drivers had to be retested but they all passed the new tests.

"You still have to have an official result through an official lab," Lindell said. "The guys that were tested negative still tested negative the second time."

Boyd Transportation was out the money by having to pay for the second round of tests, which cost between $100 to $125. But the company escaped what could've been expensive litigation if one of its untested drivers had crashed.

"If there was an accident, we could've been liable," Lindell said.

Dearth was indicted by a federal grand jury in August 2013 on charges of mail fraud and making false statements to a government agency and pleaded not guilty.

In October, Dearth pleaded guilty to 16 counts of making false statements and nine counts of mail fraud.

Dearth was ordered to surrender Sept. 6 to begin serving her prison term. She'll be on probation for one year after prison.